What was found
(CAN) APU FAIL CAUTION LIGHT ILLUMINATED DURING START ATTEMPT. APU WILL NOT START. APU STARTER GENERATOR REPLACED & APU STARTED OKAY. DURING SHOP TEAR DOWN INSPECTION OF THE STARTER GEN SHORTING & BURNING FOUND IN SPRING HOLDER & SPRING BRUSH LEADS RESULTING IN DISINTEGRATION OF THESE PARTS. SEE PICTURES ATTACHED SHOWING THE DRY CARBON OIL & SALTS ACCUMULATION, POSSIBLY FROM DRIED DEICE FLUID.